Dose setting and indicator mechanism

ABSTRACT

An injection device comprising a housing ( 112 ), and a dose selector ( 116 ) operatively connectable to a dose indicator positioned within the housing. The dose selector and the dose indicator ( 118, 119 ) are capable of cooperating to set a dose to be ejected from the injection device. The injection device further comprises a spring ( 120 ) capable of storing energy necessary for ejecting the dose from the injection device. The spring is locked to the dose indicator such that a charging force can be transferred from the dose selector to the spring via the dose indicator to increase the energy stored by the spring.

This disclosure relates to the field of dose setting and dose indicatormechanisms for injection devices, preferably to dose setting and doseindicator mechanisms having a torsion spring for assisting injection ofa dose of medicament from an injection device.

BACKGROUND

Certain injection devices are required to have a visual indicator forthe user so that the correct dose of medicament can be set and observed.This dose indicator commonly takes the form of a number sleeve, anexample of which is described in U.S. Pat. No. 8,672,898. A rotatablesleeve with numbers printed along a helical line can be inspectedthrough a window in the housing of the device, the window showing onlyone of the numbers at a time which corresponds to the dose set. However,U.S. Pat. No. 8,672,898 uses a linear compression spring. An example ofa number sleeve in an injection device using a torsion spring isdescribed in WO2014/166908.

A disadvantage of using a number sleeve to indicate the dose is that theindicator area takes up a relatively large portion of the device and isgenerally centrally located, as illustrated in FIG. 2 of WO2014/166908.Desirably, the dose indicator needs to avoid areas of the device wherethe user will grip the device, so that the user's fingers do not obscurethe dose indication.

An alternative type of dose indication is provided by an odometer or“units and tens” wheels or ciphers arrangement in place of a numbersleeve. An example is given in WO2006/045528. Two wheels, each carryingthe ten ciphers from “0” to “9” are used wherein the “tens” wheel isrotated one increment every time the “units” wheel is rotated one fullrevolution so that the two wheels between them can form all of thenumbers from “00” to “99” in a display window. An odometer has anadvantage over a number sleeve as a dose indicator in that it can belocated further rearwardly towards the proximal end of the device whereit is less likely to interfere with the user's finger position.

In WO2006/045528, when the dose setting member is rotated, a torsionspring is charged or strained, ready to deliver the appropriate dose. Atthe same time, and in parallel, the display wheels can be rotated by aplanet gear 17 to display the dose which has been set.

In WO2007/063342, dose indication is provided by a number sleeve whichis built in to a dose knob which charges the spring.

BRIEF SUMMARY OF THE DISCLOSURE

In accordance with an aspect of the present invention there is providedan injection device comprising:

-   -   a. a housing having a longitudinal axis;    -   b. an axially-depressible dose button;    -   c. a dose indicator comprising an odometer positioned within the        housing and arranged about said longitudinal axis;    -   d. a dose selector operatively connectable to the dose        indicator, the dose selector and the dose indicator being        capable of cooperating with one another to set a dose to be        ejected from the injection device; and    -   e. a spring capable of storing energy necessary for ejecting the        dose from the injection device;

wherein the spring is locked at one end to the dose indicator such thata charging force can be transferred from the dose selector to the springvia the dose indicator, when the dose selector is operatively connectedto the dose indicator, to increase the energy stored by the spring.

By coupling the spring to the dose indicator, a more accurate doseindication may be achieved. When the dose selector is rotated by a user,the dose indicator which is in series therewith serves a dual functionof both displaying the currently selected dose and also transferring thecharging force from the dose selector in order to charge the spring.

During delivery of a dose by the injection device, the spring releasesthe stored energy to deliver the dose of medicament. If the doseindicator remains coupled to the spring during delivery, the doseindicator will continue to actively reflect the current state of thespring as the spring discharges.

Embodiments of the invention are therefore advantageous over prior artarrangements in which the dose indicator is passively operated inparallel to the charging of the spring.

In certain embodiments, the dose selector is operatively connectable tothe dose indicator via a ratchet pawl, the ratchet pawl releasablyengaging the dose selector and preventing counter-rotation of the doseindicator during dose setting, the ratchet pawl being disengageable fromthe dose selector by axial depression of the dose button. In anembodiment, the charging force can be transferred from the dose selectorto the spring via the engaged ratchet pawl and dose indicator.

In certain embodiments, the spring may be a torsion spring such that thecharging force transferred to the spring is a charging torque. Theinjection device may further comprise a drive assembly having arotational to axial coupling, where the drive assembly is rotationallydrivable by the torsion spring and is arranged to provide an axial forcefor ejecting the dose from the injection device. The drive assembly maybe rotationally drivable by the torsion spring via the dose indicator.

In certain embodiments the spring may be directly locked to the doseindicator. In alternative embodiments, the spring may be locked to thedose indicator via one or more intermediate components capable oftransmitting the charging force.

Additionally or alternatively, the dose selector may be directly coupledto the dose indicator. Alternatively, the dose selector may be coupledto the dose indicator via one or more intermediate components capable oftransmitting the charging force.

The dose indicator may be marked with a sequence of numbers or symbols,where at least one of the numbers or symbols may be visible through anaperture or window in the housing.

In certain embodiments, the odometer may comprise:

a units wheel operatively connected to the dose selector so thatrotation of the dose selector also rotates the units wheel; and

a tens wheel selectively engageable with the units wheel so thatrotation of the units wheel also rotates the tens wheel.

The injection device may further comprise a medicament container, wherethe medicament container may comprise a pre-filled syringe or cartridge.The injection device may further comprise a medicament contained in themedicament container. In certain embodiments, the medicament may beselected from the group comprising: antipsychotic substances includingrisperidone, hormones, antitoxins, substances for the control of pain,immunosuppressives, substances for the control of thrombosis, substancesfor the control or elimination of infection, peptides, proteins, humaninsulin or a human insulin analogue or derivative, polysaccharide, DNA,RNA, enzymes, antibodies, oligonucleotide, antiallergics,antihistamines, anti-inflammatories, corticosteroids, disease modifyinganti-rheumatic drugs, erythropoietin, or vaccines, for use in thetreatment or prevention of rheumatoid arthritis, psoriatic arthritis,ankylosing spondylitis, ulcerative colitis, hormone deficiency,toxicity, pain, thrombosis, infection, diabetes mellitus, diabeticretinopathy, acute coronary syndrome, angina, myocardial infarction,atherosclerosis, cancer, macular degeneration, allergy, hay fever,inflammation, anaemia, or myelodysplasia, or in the expression ofprotective immunity.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are further described hereinafter, by wayof example only, with reference to the accompanying drawings, in which:

FIG. 1 shows an injection device in accordance with an embodiment of thepresent invention;

FIG. 2 is a schematic representation of a force path of an injectiondevice according an embodiment of the present invention;

FIG. 3 is an exploded view of selected injection device components alongthe force path;

FIG. 4 is a perspective view of another embodiment of the injectiondevice;

FIG. 5 is an exploded view of the injection device of FIG. 4;

FIG. 5A is a perspective view showing further detail of the dose limitnut;

FIG. 5B is a perspective view showing further detail of part of theplunger rack;

FIG. 6 is a cross-sectional view of the injection device of FIG. 4;

FIGS. 7 and 7A-7C illustrate incrementing the dose;

FIGS. 8, 8A and 8B illustrate decrementing the dose;

FIGS. 9, and 9A-9D illustrate maximum/minimum dose limiting;

FIGS. 10 and 10 a illustrate over-torque protection;

FIGS. 11,11A-11C, 12 and 12 a-12B illustrate dose delivery;

FIGS. 13, 13A and 13B illustrate a haptic feedback feature;

FIGS. 14 and 14A-14E illustrate last dose protection;

FIG. 15 is a diagrammatic summary of the key engagement points of thecomponents of the injection device of FIG. 4, at four stages of dosedelivery;

FIG. 16 summarises schematically the mechanical motion of the driveshaft 140, dose limit nut 141, worm gear 142 and plunger rack 145 duringdose setting (incrementing the dose);

FIG. 17 summarises schematically the mechanical motion of the driveshaft 140, dose limit nut 141, worm gear 142 and plunger rack 145 duringdose delivery;

FIGS. 18, 18 a and 18B show how the units wheel is incremented;

FIGS. 19, 19A and 19B show how the tens wheel is incremented;

FIG. 20 is a perspective view of another embodiment of the injectiondevice;

FIG. 21 is an exploded view of the injection device of FIG. 20;

FIG. 21A is a perspective view of the ratchet pawl, drawn to a largerscale;

FIG. 21B is a perspective view of the drive clutch, drawn to a largerscale;

FIG. 22 is a cross-sectional view of the injection device of FIG. 20;

FIG. 23 is a cross-sectional view, drawn to a larger scale, of the rearend of the injection device of FIG. 20;

FIG. 24 is a cross-sectional view, drawn to a larger scale, of thecentral portion of the injection device of FIG. 20;

FIGS. 25 and 25A-25C illustrate incrementing the dose;

FIGS. 26, 26A and 26B illustrate decrementing the dose;

FIGS. 27 and 27A-27F illustrate dose delivery;

FIG. 28 illustrates a haptic feedback feature;

FIGS. 29, 29A and 29B illustrate last dose protection;

FIG. 30 is a perspective view of the odometer mechanism;

FIG. 31 is a perspective view of the units wheel from the odometermechanism;

FIG. 32 is a perspective view of the tens wheel from the odometermechanism;

FIG. 33 is a perspective view of the shuttle lock from the odometermechanism;

FIG. 34 is a perspective view of housing features relevant to theodometer mechanism;

FIGS. 35A-35C show three stages of the odometer mechanism's operation;

FIGS. 36, 36A and 36B show further detail of the stage illustrated inFIG. 35A;

FIG. 37 shows further detail of the stage illustrated in FIG. 35B;

FIG. 38 shows further detail of the stage illustrated in FIG. 35C;

FIGS. 39A and 39B illustrate maximum/minimum dose limiting; and

FIG. 40 is a diagrammatic summary of the key engagement points of thecomponents of the injection device of FIG. 20, at six stages of dosedelivery.

DETAILED DESCRIPTION

In the present disclosure, the following terms may be understood in viewof the below explanations:

The term “injection device” may refer to a device intended for theinjection of a medicament to the body and includes devices configuredfor various delivery methods, such as intradermal, subcutaneous,intramuscular, intravenous, intraosseous, intraperitoneal, intrathecal,epidural, intracardiac, intraarticular, intracavernous, andintravitreal, which may include via a cannula, catheter or similardevice. Injection device includes syringes of all types, devices thatcontain said syringes such as auto-injectors, pen-injectors, patchinjectors and other similar devices.

The term “pen-injector” may include any device configured to deliver adose of a medicament from a cartridge.

The term “user” may refer to a medical practitioner, end user or otheruser associated therewith.

The term “coupling” may refer to a connection between components (notnecessarily a direct connection; there may be intermediate componentstherebetween) that enables a force to be transmitted between thecomponents.

The term “a rotational coupling” may refer to a coupling which enables arotational force to be transmitted between the components.

The term “operatively connectable” may refer to at least two individualcomponents which are releasably connectable together in such a way thatthe individual components can work together, for example whereinrotation of one of the individual components effects rotation of all ofthe operatively connected components.

The term “dose selector” may refer to a component or components which,when actuated by a user, enable a dose of medicament to be selected.

The term “dose indicator” may refer to a component or components whichprovide a display or indication to the user of the selected dose ofmedicament.

The term “splines” may refer to one or more ridges, ribs or otherprotrusions on one component which engage in corresponding grooves orthe like on a second component to connect the two components together.

The term “a splined connection” may refer to a connection effected byone or more splines.

The term “forward” or “forwards” may refer to a direction towards theend of the injection device from which medicament is expelled.

The term “backward”, “backwards”, “rearwards” or “rearwardly” may referto a direction away from the end of the injection device from whichmedicament is expelled.

The term “drive assembly” may refer to an assembly of components capableof using a driving force from, for example, a spring, to ejectmedicament from an injection device.

The term “backlash” may refer to a clearance caused by a gap betweenmechanical components.

The term “medicament” may include a substance in liquid or gas form. Themedicament may be selected from the group comprising of: antipsychoticsubstances including risperidone, hormones, antitoxins, substances forthe control of pain, immunosuppressives, substances for the control ofthrombosis, substances for the control or elimination of infection,peptides, proteins, human insulin or a human insulin analogue orderivative, polysaccharide, DNA, RNA, enzymes, antibodies,oligonucleotide, antiallergics, antihistamines, anti-inflammatories,corticosteroids, disease modifying anti-rheumatic drugs, erythropoietin,or vaccines, for use in the treatment or prevention of rheumatoidarthritis, psoriatic arthritis, ankylosing spondylitis, ulcerativecolitis, hormone deficiency, toxicity, pain, thrombosis, infection,diabetes mellitus, diabetic retinopathy, acute coronary syndrome,angina, myocardial infarction, atherosclerosis, cancer, maculardegeneration, allergy, hay fever, inflammation, anaemia, ormyelodysplasia, or in the expression of protective immunity.

The term “containing the medicament”, when referring to the injectiondevice, may refer to the medicament being contained within a suitablemedicament container, such as a pre-filled syringe or cartridge, withinthe injection device.

The terms “rotationally locked to” or “rotationally locked with respectto” may refer to a prevention of relative rotational movement betweentwo rotationally locked components i.e. substantially no relativerotational movement between two rotationally locked components ispossible.

The term “a force path” may refer to a path between two or more coupledcomponents via which a force can be transmitted between the components.A force path may be “interrupted” if there is a gap between the two ormore components, i.e. if they are no longer coupled. Transmission offorce between coupled components may be “held back” for example by aratchet arrangement, but in such a case the force path is not“interrupted”.

The term “a clutch” may refer to a component or feature suitable foroperatively connecting two component parts either by a positive fit e.g.with teeth, splines, grooves or the like suitable for engaging anddisengaging each other, or by a non-positive (frictional) connection ora combination thereof. Disengaging the clutch may interrupt a force pathbetween two or more coupled components.

Description of First Example Embodiment

An injection device 10 according to an embodiment of the presentinvention is shown in FIG. 1. The injection device 10 is configured todeliver a dose of medicament and extends along a longitudinal axis Lbetween a front end 10 a and a rear end 10 b of the injection device 10.The injection device 10 has a housing 12 and a needle 14 projecting fromthe housing 12 at the front end 10 a. A dose selector 16 is provided atthe rear end 10 b and is arranged to permit the selection of a desireddose of medicament for delivery through the needle 12 into an injectionsite. The housing 12 includes an aperture 12 a through which a doseindicator 18 is visible.

The dose indicator 18 is disposed within the housing 12 and displaysreference indicia, such as numbers or symbols, to indicate the level ofdose selected by the dose selector 16. The dose indicator 18 comprisesan odometer which may include a plurality of parts for indicatingindividual orders of magnitude of the selected dose. For example, theodometer may comprise a units wheel for displaying units and a tenswheel for displaying tens. The units wheel may be selectively engageablewith the tens wheel to increment the tens wheel each time the unitswheel moves through units 0 to 9.

In the preferable but non-limiting embodiment shown in FIG. 1, theaperture 12 a is provided towards the rear end 10 b of the injectiondevice 10 so that the dose indicator 18 remains visible when theinjection device 10 is handled by a user. The aperture 12 a (andunderlying dose indicator 18) may be provided elsewhere on the injectiondevice 10 in alternative embodiments. Similarly, the dose selector 16 isshown in FIG. 1 disposed at the rear end 10 b of the injection device 10and this may be advantageous insofar as being clear of the region of thehousing 12 that is likely to be gripped by a user during use of theinjection device 10. In other embodiments, the dose selector 16 may beprovided elsewhere.

FIG. 2 shows a schematic representation of a force path 26 within theinjection device 10. In particular, the force path 26 extends betweeninternal components of the injection device 10 that are arranged inseries with one another. The internal components include the doseselector 16, the dose indicator 18, a spring 20, a drive assembly 22 anda medicament container 24. As described in further detail below, thespring 20 is configured to provide a drive force to the drive assembly22 such that the drive assembly 22 may act to dispense medicament fromthe medicament container 24. A dose button (not shown), which isoptionally axially-depressible, initiates dose delivery.

The dose selector 16 is coupled to the dose indicator 18 such that theindicated level of dose changes in response to manipulation of the doseselector 16. In one example, the reference indicia comprise a series ofnumbers and rotation of the dose selector 16 about the longitudinal axisL causes the number aligned with the aperture 12 a to change accordingto the degree of rotation of the dose selector 16. Rotation of the doseselector 16 about the longitudinal axis L in one direction may cause thenumbers to appear to increase when viewed through the aperture 12 a,whereas rotation of the dose selector 16 about the longitudinal axis Lin the opposite direction may cause the numbers to decrease when viewedthrough the aperture 12 a.

The dose indicator 18 is coupled to the spring 20 such that a chargingforce can be transmitted from the dose selector 16 to the spring 20 viathe dose indicator 18 in order to charge the spring 20. The spring 20 ischarged when a force is applied to the spring 20 so as to elasticallydeform the spring 20, and the resulting elastic energy is stored by thespring 20 (i.e. it is prevented from elastically relaxing during astorage phase). Therefore, charging the spring 20 involves increasingthe energy stored by the spring 20.

The spring 20 is coupled to the drive assembly 22 and is arranged toprovide a driving force thereto when energy stored by the spring 20 isreleased. The drive assembly 22 acts to expel medicament from themedicament container 24. In certain embodiments, the medicamentcontainer 24 may be a syringe, vial or cartridge having a barrel and astopper moveable in the barrel. In such embodiments, the drive assembly22 may act to move the stopper so as to expel medicament through anopening in the barrel. In certain embodiments of the invention, themedicament cartridge may or may not be connected to a needle.

In certain embodiments, the spring 20 may be coupled to the driveassembly 22 via the dose indicator 18 and/or dose selector 16 (i.e.backwards along the force path 26 from the spring 20).

In embodiments where the spring 20 is a torsion spring, the spring 20 ischarged by applying a torque to wind the spring 20 and elastic energymay be stored by the spring 20 and subsequently released as torque. Insuch embodiments, the force path 26 extending (at least) between thedose indicator 18 and the drive assembly 22 may be a torque path. Thatis, torque may be provided to the spring 20 from the dose indicator 18and provided to the drive assembly 22 from the spring 20. In certainembodiments, the torque path extends from the dose selector 16 to thedrive assembly 22 and the drive assembly 22 includes a rotational toaxial coupling that is capable of then providing an axial force to astopper in a barrel of the medicament container to expel medicamenttherefrom.

In embodiments where the spring 20 is a compression spring, the spring20 may be charged by applying an axial force to compress the spring 20and elastic energy may be stored by the spring 20 and subsequentlyreleased as an axial force.

In certain embodiments, the force path 26 may include one or more torquepaths and/or one or more axial force paths, where one or more rotationalto axial couplings are employed to switch between rotational and axialforces along the force path 26. Indeed, in certain embodiments, one ormore intermediate components may be provided between any of thecomponents shown in FIG. 2.

The amount of elastic energy stored by the spring 20 dictates themagnitude of the dose that is capable of being delivered. As such, thedose indicator 18 indicates the degree to which the spring 20 ischarged, and thereby indicates the dose that will be delivered once theinjection device 10 is actuated.

FIG. 3 shows an exploded view of the dose selector 16, the doseindicator 18 and the spring 20 arranged along the longitudinal axis Laccording to an embodiment of the invention. The dose selector 16 hasfirst engaging components in the form of a first plurality of teeth 16a. The dose indicator 18 of FIG. 3 comprises an odometer that isrotatable about the longitudinal axis L and includes a series of numberson an outer surface. The dose indicator 18 has second engagingcomponents in the form of a second plurality of teeth 18 a that arecomplementary to the first plurality of teeth 16 a and configured toengage therewith. Engagement between the first plurality of teeth 16 aand second plurality of teeth 18 a forms a rotational coupling tooperatively connect the dose indicator 18 to the dose selector 16 suchthat torque may be transferred therebetween.

In an assembled state, a first end 20 a of the spring 20 is rotationallyfixed to the dose indicator 18 so that the dose indicator 18 isrotationally coupled to the spring 20. For example, during assembly, thefirst end 20 a of the spring 20 may be hooked through an aperture of thedose indicator 18, hooked to a projection of the dose indicator 18 orotherwise attached to the dose indicator 18. When the spring 20 isrotationally coupled to the dose indicator 18, torque is transferablefrom the dose selector 16 to the spring 20 via the dose indicator 18. Asecond end 20 b of the spring may be attached to the drive assembly 22(not shown in FIG. 3), and the drive assembly 22 may prevent rotation ofthe second end 20 b of the spring 20 when the drive assembly 22 is notin an actuated state. In alternative embodiments, the second end 20 b ofthe spring 20 may be rotationally held by a portion of the housing 12 orother component within the housing 12, and the drive assembly 22 may becoupled to the spring 20 at the first end 20 a or via one or morecomponents along the force path that extends between the dose selector16 and the spring 20 (e.g. via the dose indicator 18 or the doseselector 16 itself).

With the second end 20 b of the spring 20 rotationally held, torquetransferred to the spring 20 from the dose selector 16 and doseindicator 18 will cause the spring 20 to be wound up (i.e. charged),thereby increasing the amount of elastic energy stored in the spring 20.A ratchet or other non-return mechanism may be employed to prevent thewound spring 20 from unwinding prior to use. That being said, theratchet or other non-return mechanism may permit the deliberateincremental unwinding of the spring 20 through rotation of the doseselector 16 (i.e. when rotated in the opposite direction to thedirection required to charge the spring 20). Given the rotationalcoupling between the dose selector 16, the dose indicator 18 and thespring 20, the ratchet or other non-return mechanism will also preventunintended rotation of the dose selector 16 and dose indicator 18 aboutthe longitudinal axis L due to unwinding of the spring 20.

Given that the dose indicator 18 forms an essential and integral part ofthe force path between the dose selector 16 and the spring 20, the doseindicator 18 actively reflects the charging state of the spring 20.Similarly, if the dose indicator 18 remains coupled to the spring 20during discharging of the stored energy (i.e. during delivery of a doseof medicament), the dose indicator 18 will continue to actively reflectthe state of the spring 20. For example, the number indicated by thedose indicator 18 may change to zero when delivery of a dose ofmedicament is complete, thereby reflecting the discharged state of thespring 20.

Description of Second Example Embodiment

A further, non-limiting, embodiment of an injection device according tothe present invention is illustrated in FIGS. 4-19B.

Referring to FIGS. 4-6, the injection device 100 includes a housing 112,a dose selector 116, a dose button 130 and dose button spring 131, aunits wheel 118, a tens wheel 119, a dose indicator spring 117, a driveshaft 140, a drive spring 120, a dose limit nut 141, a worm gear 142, aworm gear support 143 and a worm gear rotational lock 144, all locatedconcentrically about a common longitudinal axis L. The axis L extendsbetween a front end 100 a and a rear end 100 b of the injection device100.

The injection device 100 has a medicament cartridge 124 supported in acartridge holder 125 at the front end 100 a of the injection device 100.The cartridge 124 is sealed by an axially-moveable cartridge stopper 126at its rear end. The cartridge and cartridge holder are locatedconcentrically about a second longitudinal axis Lc, such that thecartridge is offset from the main housing 112, with L and Lc offset fromone another as shown in FIG. 6.

The dose button 130 is biased rearwardly by the dose button spring 131.The dose selector 116 is provided at the rear end 100 b of the injectiondevice 100 and is arranged to permit the selection of a desired dose ofmedicament for delivery from the medicament cartridge 124 into aninjection site. The dose selector 116 is axially constrained withrespect to the housing 112 but is rotatable with respect thereto, aboutaxis L. The dose selector 116 is rotationally coupled to the drive shaft140 via pawl features 115, visible in FIG. 7A, which engage splines 149on the drive shaft 140. The housing 112 is provided with teeth 113(visible in FIG. 7A) on an inside surface thereof for engaging ratchetarms 146 on the drive shaft 140. Tabs 114 on the dose selector 116 arecapable of depressing the drive shaft ratchet arms 146 when required, asshown in FIG. 8B. The housing 112 is also provided with ramp features111 (visible in FIG. 12A) which facilitate disengagement of the ratchetarms 146 from the inside surface of the housing 112 when required.

A dose indicator is disposed within the housing 112 and displaysreference indicia, such as numbers or symbols, to indicate the level ofdose selected by the dose selector 116. The housing 112 includes anaperture 112 a through which the dose indicator is visible. The doseindicator comprises the units wheel 118 for displaying units and thetens wheel 119 for displaying tens. The units wheel 118 is selectivelyengageable with the tens wheel to increment the tens wheel each time theunits wheel moves through units 0 to 9. The units wheel 118 isrotationally coupled to the drive shaft 140.

As with the first embodiment, described with reference to FIGS. 1-3,biasing means in the form of dose indicator spring 117 biases the unitswheel 118 and tens wheel 119 axially rearwardly in the housing.

The housing 112 has features on an inside surface thereof for engagingwith the units wheel 118 and the tens wheel 119.

An internal surface of the housing 112 is provided with a tens housingfeature 108 selectively engageable with the tens wheel 119 to preventrotation thereof. The tens housing feature comprises one or more axiallyforwardly extending formations 108 which may be equally spaced aroundthe internal circumference of the housing 112. The formations 108 engagewith corresponding axially rearwardly extending formations 119 b at therear of the tens wheel 119. The tens housing feature formations 108 andthe tens wheel formations 119 b may be teeth, notches, castellations orany other shaped formations that, when engaged together, preventrelative rotation between the tens wheel 119 and the housing 112.

An internal surface of the housing 112 is provided with a units housingfeature 107 capable of moving the units wheel axially-forward againstsaid biasing means 117. The units housing feature is an axiallyforwardly extending formation 107 having a cam surface which can engagewith an axially rearwardly extending formation 118 b on the units wheel118 in order to push the units wheel 118 axially forwards.

Teeth 118 a on the front end of the units wheel 118 are engageable withcorrespondingly shaped teeth 119 a at the rear end of the tens wheel119. On the tens wheel 119, the teeth 119 a (for engaging the unitswheel) and the tens wheel formations 119 b (for engaging the housing)may be concentrically arranged around the longitudinal axis of theinjection device, with the teeth 119 a radially inward of the formations119 b.

The drive spring 120 is a torsion spring which is fixed at one end withrespect to the housing 112 and rotationally coupled at its other end tothe drive shaft 140 via the units wheel 118.

A worm gear arrangement is provided which comprises a worm gear 142meshed with a toothed plunger rack 145 located within the housing 112.During dose delivery, the worm gear 142 drives the plunger rack 145forward which, in turn, pushes against the cartridge stopper 126 todeliver a dose of medicament. A splined clutch 150 at the forward end ofthe drive shaft 140 enables the worm gear 142 and drive shaft 140 to besplined together during dose delivery but not during dose setting andthis will be described in more detail later. In FIG. 6, the worm gearrotational lock 144 is engaged in the forward end of the worm gear 142,preventing rotation thereof. The worm gear rotational lock 144 iscapable of being pushed axially forward by the drive shaft 140 in orderto disengage the lock from the worm gear 142.

The dose limit nut 141 is keyed to the drive shaft 140 so that they arerotationally coupled but not axially coupled. The dose limit nut 141 isengaged with the teeth of the plunger rack 145 and can travel axiallyforward and backward along the plunger rack 145 as the dose isincremented or decremented respectively. The axial range within whichthe dose limit nut 141 can travel along the plunger rack 145 isdetermined by dose limit nut endstop features 141 a, 141 b which canengage features on the plunger rack thread to serve as endstops for thetravel of the dose limit nut 141. FIG. 5A shows the maximum dose limitnut endstop feature 141 a and the minimum dose limit nut endstop feature141 b in more detail. Endstops 141 a, 141 b are able to engage features147, 148 respectively on the plunger rack 145 (FIG. 5B). These features147, 148 are preferably changes in the depth of or formations on theplunger rack thread, past which the dose limit nut 141 cannot travel.During dose delivery, the dose limit nut 141 rotates about axis L withthe drive shaft 140 to which it is keyed, but it does not move axiallywith respect to the plunger rack 145 with which it is engaged, thusalways keeping the dose limit nut 141 within the range defined by themax/min dose endstops.

The operation of the respective features of the injection device 100will now be described in more detail below.

Dose Setting—Incrementing the Dose

With the injection device 100 in the configuration shown in FIG. 7, theuser grips the dose selector 116 and rotates it clockwise about axis L,with respect to the housing 112, in order to increment the dose andcharge the drive spring 120. As the dose selector 116 is turnedclockwise, the pawl features 115 engaging the splines 149 on the driveshaft 140 cause the drive shaft 140 to also be driven clockwise, asshown in FIG. 7A.

While the dose is being incremented, the ratchet arms 146 on the driveshaft 140 engage with the teeth 113 on the inside surface of the housing112 to prevent un-winding by the drive spring 120, as shown in FIG. 7B.

As shown in FIG. 7C, the drive shaft 140 is splined to the units wheel118 which charges or torques up the drive spring 120. In other words,torque is transferred from the dose selector 116 to the drive spring 120directly through the dose indicator, i.e. the units wheel 118.

Dose Setting—Decrementing the Dose

When it is desired to decrement the selected dose, the dose selector 116is turned anti-clockwise. As shown in FIG. 8A, as the dose selector 116is turned anti-clockwise, there is a small amount of backlash at point Asuch that the dose selector 116 can rotate slightly with respect to thedrive shaft 140. This small relative movement is sufficient to allow thetabs 114 on the dose selector 116 to depress the drive shaft ratchetarms 146 so that they can click past the housing teeth 113, allowing thedrive spring to unwind slightly before the ratchet arms 146 catch againon the next housing tooth 113. This is represented in FIG. 8B. Eachdecrement preferably equates to 1 IU (“international unit”) ofmedicament.

Dose Setting—Maximum/Minimum Dose

As the drive shaft 140 is rotated during dose setting, the dose limitnut 141, which is keyed to the drive shaft 140, is also rotated (FIG.9A). The dose limit nut 141 travels forwards when incrementing the doseand rearwards when decrementing the dose (FIG. 9B). The dose limit nut141 is engaged in the thread of the plunger rack 145. Endstop features147, 148 are located on the plunger rack 145, past which the dose limitnut 141 cannot travel (FIG. 9C). These endstop features 147, 148 may bechanges in the depth of the thread. As shown in FIG. 9D, when the doselimit nut 141 rotates into a position wherein the dose limit nut endstopfeature 141 a engages feature 147 on the plunger rack 145, a rotaryendstop occurs, preventing further rotation of the dose limit nut 141 sothat a dose of medicament greater than the desired maximum dose ofmedicament cannot be set. Limiting the travel of the dose limit nut 141sets the maximum and minimum doses of medicament that can be set duringdose setting, preferably 100 IU and 0 IU respectively.

Dose Setting—Over Torque

As shown in FIG. 10A, in the event the user applies too much force (overtorque) to the dose selector 116 in either rotational direction, thedose selector pawl features 115 will flex radially outwardly to allowthem to skip past splines 149 on the drive shaft 140. Preferably theinterfacing surface areas of the pawl features 115 and/or splines 149act as a cam lever, preferably having a matching angle and/or a definedstatic and dynamic surface friction at the interface surface. Theover-torque for flexing out the dose pawl features 115 to skip pastspline 149 is preferably at least 10% higher than the torque requiredfor dialing up (incrementing) or dialing down (decrementing) the doseindicator 18, 118. The dialing up torque can be 30 to 80 Nmm, preferablyless than 60 Nmm, more preferably 30 to 50 Nmm. The dialing down torquecan be 20 to 60 Nmm, preferably less than 50 Nmm, more preferably 30 to40 Nmm. The over-torque in the dialing up direction may be different tothe over-torque in dialing down direction. The outward flexing forceand/or strength of one flexible pawl arm 115 could be lower compared toa second flexible pawl arm.

FIG. 16 summarises schematically the mechanical motion of the driveshaft 140, dose limit nut 141, worm gear 142 and plunger rack 145 duringdose setting (incrementing the dose). The drive shaft 140 rotatesclockwise. The dose limit nut 141 rotates clockwise and advancesforwards with respect to the plunger rack 145.

Dose Delivery

To initiate dose delivery, the user presses the dose button 130 againstthe bias of the dose button spring 131 as shown in FIG. 11A. This pushesthe drive shaft 140 axially forwards. Although the drive shaft 140 issplined to the units wheel 118, it is free to slide axially with respectthereto (FIG. 11B).

As the drive shaft 140 advances, at its forward end, the splined clutch150 between the drive shaft and the worm gear 142 engages (FIG. 11C,FIG. 15—Worm Gear Clutch 150). Preferably the drive element, inparticular the worm gear 142 and the drive shaft 140 engage after 0.5 mmto 1.5 mm advancement of the dose button 130, more preferably after 0.8mm to 1.2 mm advancement of the dose button 130. Once the clutch 150 hasstarted to engage, the ratchet arms 146 on the drive shaft 140 begin todisengage from the inside surface of the housing 112 aided by rampfeatures 111 (FIG. 12A, FIG. 15—Hold Ratchet). Preferably the holdratchet, in particular the ratchet arms 146 on the drive shaft 140 startto disengage from the structured, in particular toothed surface of thehousing 112 after 1.5 mm to 2.5 mm advancement of the dose button 130,more preferably after 1.6 mm to 1.9 mm advancement of the dose button130. Also, as the drive shaft 140 moves forward, the splines 149coupling the drive shaft 140 to the dose selector 116 disengage (FIG.12B, FIG. 15—Over torque ratchet). Preferably the over torque ratchet,in particular the drive shaft splines 149 on the drive shaft 140 startto disengage from the dose selector pawls 115 after 1.5 mm to 3.5 mm ofadvancement of the dose button 130, more preferably after 2 mm to 3 mmadvancement of the dose button 130. The dose indicator and drive shaft140 are now free to rotate about longitudinal axis L.

The drive spring 120 drives the units wheel 118 to rotate aboutlongitudinal axis L. The units wheel 118 drives the drive shaft 140which drives the worm gear 142.

FIG. 17 summarises schematically the mechanical motion of the driveshaft 140, dose limit nut 141, worm gear 142 and plunger rack 145 duringdose delivery. The drive shaft 140, dose limit nut 141 and worm gear 142all rotate anti-clockwise. Only the plunger rack 145 advances forwards.During dose delivery, the dose limit nut 141 rotates with the driveshaft 140 but does not move axially with the plunger rack 145. The doselimit nut 141 and the drive worm gear 142 preferably have the samethread pitch.

The worm gear 142 actuates the plunger rack 145 to move axially forwardscausing the cartridge stopper 126 to be driven into the cartridge inorder to expel medicament thus delivering the selected dose.

When the dose button 130 is released, the dose button spring 131 returnsthe dose button 130 and drive shaft 140 to their original startingpositions. This axially rearward movement disengages the worm gearclutch 150 and re-engages the drive shaft ratchet arms 146 with thehousing 112 thereby stopping dose delivery.

Dose Delivery—Haptic Feedback

During dose delivery, the drive shaft ratchet arms 146 run(rotationally) on a relatively smooth track 110 on the inside surface ofthe housing 112 (FIG. 13A). Optionally, this track could be modified toinclude ridges 109 which would provide audible/haptic feedback to theuser during dose delivery (FIG. 13B). The ridges 109 are convenientlyplaced relatively close to the user's fingers.

Last Dose Protection

When the medicament cartridge 124 is relatively empty, after severaldoses have already been delivered therefrom, it is undesirable for theuser to be able to select a dose that is larger than the availablequantity of medicament remaining. Last dose protection is provided todeal with this situation. Conveniently, the last dose protection isprovided by the same feature as the max/min dose limiting i.e. the doselimit nut 141.

As shown in FIG. 14, after several doses have been delivered, theplunger rack 145 and dose limit nut 141 have advanced axially forwardssuch that the dose limit nut 141 is approaching the worm gear 142. Whenthere is less than a predetermined amount (e.g. 100 IU) of medicamentavailable, the worm gear 142 serves as an endstop, stopping the doselimit nut 141 from moving further forwards and before the maximum doselimit feature 147 on the plunger rack 145 is reached (FIG. 14A).Preferably, it is the dose limit nut endstop feature for maximum doselimiting 141 a which engages the worm gear 142. If the user tries toincrement the dose further, torque is transmitted through the dose limitnut 141 into the worm gear 142, the torque being reacted to by the wormgear rotational lock 144 (FIG. 14B). As such, the worm gear 142 isunable to rotate due to rotational engagement with the rotational lock144.

During dose delivery, when the drive shaft 140 is moved axiallyforwards, the worm gear clutch 150 is engaged before the worm gearrotational lock 144 is disengaged (FIG. 14C). The axially-forwardmovement of the drive shaft 140 causes its forward end to push the wormgear rotational lock 144 out of the front of the worm gear 142. With theworm gear rotational lock 144 disengaged, the worm gear 142 is free torotate, driven by the drive shaft 140 (FIG. 14D). Once dose delivery isfinished, the drive shaft 140 moves rearwardly. The worm gear rotationallock 144 re-engages, before the worm gear clutch 150 is disengaged (FIG.14E).

FIG. 15 is a diagrammatic summary of the key engagement points of theinjection device components, at four stages of dose delivery.

Dose Display

As already described above, during dose selection the user rotates thedose selector 116 which also drives the drive shaft 140 around. Ratchetarms 146 interact with teeth 113 in the housing 112 to prevent unwinding(FIG. 18A). The drive shaft 140 is splined to the units wheel 118 which,as it turns, increments the displayed unit (FIG. 18B).

The units wheel 118 and tens wheel 119 are biased rearwardly by doseindicator spring 117. Twice per revolution of the units wheel 118, theunits wheel 118 is moved axially forwards by the cam surface of theunits housing feature 107 engaging with the formation 118 b on the unitswheel 118. This axially forward movement causes the teeth 118 a of theunits wheel 118 to engage with the teeth 119 a of the tens wheel 119(FIG. 19A). Continued forward axial movement of the units wheel 118pushes the formations 119 b of the tens wheel 119 away from the tenshousing feature 108, so that the tens wheel 119 is free to rotate withrespect to the housing 112, allowing the tens wheel 119 to be drivenaround by the units wheel 118 by one increment (FIG. 19B).

In a preferred embodiment, the selectable and settable dose range is 1to 100 IU, with a minimum dose setting of 1 IU, wherein per 360 degreerotation of the dose selector 116, 20 to 30 IU may be set. As the unitswheel 118 and tens wheel 119 arrangement permits indication of the setIU dose by two digits, a much larger font size for the indicated dosenumber is usable, thus the arrangement affords better readability of theset dose and usability of the injection device 10, 100.

As with the first embodiment, described with reference to FIGS. 1-3, thedrive spring 120 is coupled to the units wheel 118 (via the drive shaft140 splined to the units wheel 118) such that a charging force can betransferred from the dose selector 116 to the spring 120 via the unitswheel 118 to increase the energy stored by the spring 120. Such acoupling is preferably achieved by locking one end of the drive spring120 to the units wheel 118 and winding the drive spring 120 when theunits wheel 118 is turned during dose selection. The other end of thedrive spring 120 is fixed against rotational movement, preferably beingfixed to a part of the housing 112. By coupling the spring 120 to theunits wheel 118, a more accurate dose indication may be achieved. Whenthe dose selector 116 is rotated by a user, the dose indicator (unitswheel 118 and tens wheel 119), which is in series therewith serves adual function of both displaying the currently selected dose and alsotransferring the charging force from the dose selector in order tocharge the drive spring 120.

Description of Third Example Embodiment

A further, non-limiting, embodiment of an injection device according tothe present invention is illustrated in FIGS. 20-40.

Referring to FIGS. 20-24, the injection device 200 includes a housing212, a dose selector 216, a dose button 230 and dose button spring 231,a units wheel 218, a tens wheel 219, a ratchet pawl 217, a housing topcap 221, an odometer shuttle lock 222, a drive spring 220, a drivesleeve 240, a last dose nut 241, a drive clutch 250, a drive clutchspring 251, a leadscrew nut 252, a leadscrew 253 and a thrust bearing254, all located concentrically about a common longitudinal axis L. Theaxis L extends between a front end 200 a and a rear end 200 b of theinjection device 200.

The injection device 200 has a medicament cartridge 224 supported in acartridge holder 225 at the front end 200 a of the injection device. Aneedle or needle hub unit (not shown) can be connected to the cartridgeholder. The cartridge is sealed by an axially-moveable cartridge stopper226 at its rear end.

The dose button 230 is biased rearwardly by the effect of the dosebutton spring 231 between the housing 212 and front end of the drivesleeve 240 with which the dose button 230 is axially engaged. The doseselector 216 is provided at the rear end 200 b of the injection device200 and is arranged to permit the selection of a desired dose ofmedicament for delivery from the medicament cartridge 224 into aninjection site. The dose selector 216 is axially constrained withrespect to the housing 212 but is rotatable with respect thereto, aboutaxis L. The dose selector 216 is used to set the dose by increasing therotational preload of the drive spring 220 which is prevented fromunwinding by the ratchet pawl 217 which engages between the housing 212and the units wheel 218.

The ratchet pawl 217 (best seen in FIG. 21A) includes a plurality ofratchet fingers 217 a which, in the assembled injection device 200,extend generally axially rearwardly to engage with the units wheel 218as shown in FIG. 25C. The ratchet pawl 217 also includes ratchet arms217 b which, in the assembled injection device 200, engage with teeth213 on the inside surface of the housing 212 to prevent un-winding ofthe drive spring 220, as shown in FIG. 25B, while the dose is beingincremented.

A dose indicator is disposed within the housing 212 and displaysreference indicia, such as numbers or symbols, to indicate the level ofdose selected by the dose selector 216. The housing 212 includes anaperture 212 a through which the dose indicator is visible. The doseindicator comprises the units wheel 218 for displaying units and thetens wheel 219 for displaying tens and the odometer shuttle lock 222.The units wheel 218 is intermittently coupled to the odometer shuttlelock 222 which is always rotationally coupled to the tens wheel 219. Thetens wheel 219 has maximum and minimum dose limit features in the formof rotational endstops 271, 272 respectively, which can engage alimiting rib 290 in the housing 212 to keep the selected dose within therange defined by the maximum and minimum doses. This max/min doselimiting will be described in more detail later.

With reference to FIGS. 30-34, the dose indicator is an odometercomprising a units wheel 218, a tens wheel 219 and an odometer shuttlelock 222. The units wheel 218 has units numbers 260 around thecircumference thereof, comprising two consecutive series of the numbers0-9. Two drive dogs 261 are located 180 degrees apart on the internalsurface of the forward end of the units wheel 218 and two engagementsplines 262 are also located 180 degrees apart from one another. Thesets of drive dogs 261 and engagement splines 262 may be rotationallyoffset from one another by approximately 90 degrees. In an alternativeembodiment the units wheel 218 may comprise one consecutive series ofthe numbers 0-9 around its circumferential surface, and one drive dog261. The units wheel 218 may comprise one or more than two engagementsplines 262, the engagement splines 262 rotationally arranged to beengageable with the shuttle lock rear teeth 283. The drive dogs 261 haveangled faces which, when engaging corresponding angled faces 282 on theshuttle lock 222, cause a camming action that can move the shuttle lock222 axially.

Tens wheel 219 has tens numbers 270 around the circumference thereof,comprising a series of the numbers 0-10. The forward end of the tenswheel 219 includes maximum and minimum dose limit features 271, 272, inthe form of rotary endstops which can each engage a max/min limit rib290 on the internal surface of the housing 212. The internal surface ofthe tens wheel 219 includes a key 273 for engaging with the shuttle lock222.

The shuttle lock 222 is a generally cylindrical component having aforward section of largest diameter with double-ended peripheral teeth280 at the forward end thereof having angled faces which can alternatelyengage dogs 291 and engagement ribs 292 on the interior of the housing212. The angled faces cause a camming action that can move the shuttlelock 222 axially.

In general terms, the function of the housing dogs 291, housingengagement ribs 292 and units wheel drive dogs 261 is to enable theshuttle lock 222 to move alternately between two axial positions, aswill be explained in more detail later.

An axially-extending keyway 281 is provided for engaging the key 273 onthe tens wheel 219 in order to rotationally lock the tens wheel 219 andshuttle lock 222 together whilst permitting axial movement therebetween.In alternative embodiments, the key may be provided on the shuttle lock222 and the axially-extending keyway may be provided on the tens wheel219.

The rear section of the shuttle lock 222 is of smaller diameter andincludes dogs 282 at the rear end thereof, located 180 degrees apartfrom one another which can engage with the drive dogs 261 of the unitswheel 218.

The rear surface of the shuttle lock 222 is provided with a series ofaxially-extending shuttle lock rear teeth 283. The number of teeth 283corresponds with the number of units of medicament available perrotation of the units wheel 218 (in this case 20). Depending upon therelative axial positions of the units wheel 218 and the shuttle lock222, the engagement splines 262 on the units wheel 218 can either beengaged with the shuttle lock rear teeth 283, or not engaged with theshuttle lock rear teeth 283.

FIG. 34 shows the portion of the internal surface of the housing 212which interacts with the odometer mechanism. The aperture 212 a throughwhich the dose is displayed can be seen. The illustrated portion of thehousing includes an internally-projecting max/min limit rib 290, twodogs 291 for engaging the shuttle lock 222 and three engagement ribs 292for engaging the shuttle lock 222. FIG. 34 is shown partly incross-section; the pointed ends of dogs 291 are at the same axialposition and are located 180 degrees apart on the internal surface ofthe housing 212 (half of the housing 212 has been removed from FIG. 34).

As illustrated in FIG. 34, one of the dogs 291 for engaging the shuttlelock 222 may be located at one end of the max/min limit rib 290 suchthat both functions can be performed by the same component on theinternal surface of the housing 212.

The drive spring 220 is a torsion spring which is fixed at one end withrespect to the housing 212 and engaged at its other end to the unitswheel 218.

The drive clutch 250, best seen in FIG. 21B, is generally circular withformations (uppermost in FIG. 21B) which, in the assembled injectiondevice 200, extend in a direction towards the rear of the device. Thedrive clutch spring 251 biases the medicament cartridge 224. The housing212 is provided with forward-facing clutch engaging features 215 which,in the position shown in FIG. 25, engage the clutch 250 so that they arerotationally locked together. The clutch 250 can be disengaged from theclutch engaging features of the housing 215 by forward axial movement ofthe clutch 250, caused by forward movement of the drive sleeve 240. Ahaptic feedback arm 250 a is provided on the front face of the driveclutch 250 (the underside in FIG. 21B).

The operation of the respective features of the injection device 200will now be described in more detail below.

When the dose button 230 is depressed, firstly the drive clutch 250 isdecoupled from the housing 212 and coupled to the drive sleeve 240.Secondly, the ratchet pawl 217 is decoupled from the units wheel 218.Decoupling of the ratchet pawl 217 from the units wheel 218 allows thedrive spring 220 to rotate the units wheel 218 and drive sleeve 240,which are rotationally coupled together, about the longitudinal axis L.

Rotation of the drive sleeve 240 causes the drive clutch 250 to rotatewhich, in turn, rotates the leadscrew 253 to which the drive clutch 250is splined.

Rotation of the leadscrew 253 causes it to advance axially forwardstowards the front end 200 a of the injection device 200 because of theengagement of the leadscrew thread with the thread of the leadscrew nut252. The leadscrew nut 252 is rotationally and axially fixed withrespect to the housing 212.

During dose setting, the last dose nut 241 is rotationally fixed withrespect to the housing 212 via the leadscrew 253. The last dose nut 241can translate axially up and down the thread inside the drive sleeve 240due to rotation of the drive sleeve 240 when the dose is being set.Translation of the last dose nut 241 inside the drive sleeve 240 islimited by a rotational stop feature on the drive sleeve 240 whichlimits the travel of the last dose nut 241 to a position correspondingwith the maximum dispense volume of the injection device 200.

During dose delivery, the drive sleeve 240, leadscrew 253 and last dosenut 241 all rotate together and there is no axial translation of thelast dose nut 241 with respect to the drive sleeve 240.

Dose Setting—Incrementing the Dose

With the injection device 200 in the configuration shown in FIG. 25, theuser grips the dose selector 216 and rotates it clockwise about axis L,with respect to the housing 212, in order to increment the dose andcharge the drive spring 220. As the dose selector 216 is turnedclockwise, the dose selector 216 is engaged with the ratchet pawl 217,causing it to rotate with the dose selector 216. The ratchet pawl 217drives the units wheel 218 clockwise because of ratchet fingers 217 aengaging ribs 218 a of the units wheel 218, as shown in FIG. 25A. Thedrive spring 220 is hooked into the back of the units wheel 218 and istherefore tightened as the units wheel 218 is rotated. In other words,torque is transferred from the dose selector 216 to the drive spring 220directly through the dose indicator, i.e. the units wheel 218.

While the dose is being incremented, the ratchet arms 217 b on theratchet pawl 217 engage with teeth 213 on the inside surface of thehousing 212 to prevent un-winding of the drive spring 220, as shown inFIG. 25B.

When the dose selector 216 reaches a maximum, minimum or last doselimit, the ratchet fingers 217 a flex radially outwardly and skip pastthe ribs 218 a of the units wheel 218 (FIG. 25C).

Dose Setting—Decrementing the Dose

When it is desired to decrement the selected dose, the dose selector 216is turned anti-clockwise. As shown in FIG. 26A, as the dose selector 216is turned anti-clockwise, there is a small amount of backlash at point Asuch that the dose selector 216 can rotate slightly with respect to theratchet pawl 217. This small relative movement is sufficient to allowtabs 214 on the dose selector 216 to depress the ratchet arms 217 b sothat they can click past the housing teeth 213, allowing the drivespring to unwind slightly before the ratchet arms 217 b catch again onthe next housing tooth 213. The tabs 214 may be tooth-shaped formationsprojecting radially-inwardly from an internal surface of the doseselector 216. This is represented in FIG. 26B. Each decrement preferablyequates to 1 IU (“international unit”) of medicament.

Dose Delivery

To initiate dose delivery, the user presses the dose button 230 againstthe bias of the dose button spring 231 as shown in FIG. 27. This pushesthe drive sleeve 240 axially forwards. Although the drive sleeve 240 isrotationally locked to the units wheel 218, it is free to slide axiallywith respect thereto (FIG. 27B).

As the drive sleeve 240 advances, its forward end engages the rearsurface of the drive clutch 250. The drive clutch 250 disengages fromthe clutch engaging features 215 on the inside surface of the housing212 (FIG. 27C). Once the drive clutch 250 is fully engaged with thedrive sleeve 240, the dose button 230 disengages the ratchet pawl 217from the units wheel 218 (FIG. 27D). The units wheel 218 is now free torotate the drive sleeve 240 and therefore also the drive clutch 250about longitudinal axis L. The drive clutch 250 is splined to theleadscrew 253 (FIG. 27E).

Therefore the leadscrew 253 now rotates and is caused to advance axiallydue to threaded engagement with the leadscrew nut 252. The thrustbearing 254 advances the cartridge stopper 226 into the cartridge, inorder to expel medicament to deliver the selected dose (FIG. 27F).

When the dose button 230 is released, the dose button spring 231 returnsthe dose button 230 and drive sleeve 240 to their original startingpositions. This axially rearward movement disengages the drive clutch250 and re-engages the ratchet arms 217 b with the housing 212 therebystopping dose delivery.

Dose Delivery—Haptic Feedback

Referring to FIG. 28, during dose delivery haptic feedback occursbetween the drive clutch 250 and the leadscrew nut 252 when the driveclutch 250 is spinning, by virtue of the haptic feedback arm 250 a onthe drive clutch clicking over axially-rearwardly-facing teeth on theleadscrew nut 252.

Last Dose Protection

When the medicament cartridge 224 is relatively empty, after severaldoses have already been delivered therefrom, it is undesirable for theuser to be able to select a dose that is larger than the availablequantity of medicament remaining. Last dose protection is provided todeal with this situation. Last dose protection is provided by the lastdose nut 241.

As shown in FIG. 29A, the last dose nut 241 moves axially forwards andbackwards on the thread inside the drive sleeve 240 during doseincrementing and decrementing. When there is less than a predeterminedamount (e.g. 100 IU) of medicament remaining in the cartridge 224, thelast dose nut 241 stops against a rotary endstop 240 a at the rear ofthe drive sleeve thread.

Engagement of the last dose nut 241 with the endstop 240 a means that,should the user attempt to wind the dose selector 216 beyond theremaining dose, the over-torque protection is actuated, preventing theuser from damaging the device (FIG. 29B). The ratchet fingers 217 adisengage from the units wheel 218 as previously described in relationto FIG. 25C.

Dose Display

FIGS. 35A-35C show, in schematic form, the three stages of the odometermechanism's operation. More detail of the respective stages is shown inFIGS. 36-38.

In stage 1 (FIGS. 35A, 36, 36A and 36B) for dose 0-9, the units wheel218 is free to turn. Rotation of the dose selector 216 causes the doseto increment through doses 0-9. For doses 0-9, there is no engagementbetween the units wheel drive dogs 261 and the shuttle lock dogs 282(FIG. 36B). The tens wheel 219 is rotationally locked but is axiallymoveable relative to the shuttle lock 222 because the key 273 is engagedin the keyway 281 (see FIG. 30). The shuttle lock 222 is rotationallylocked to the housing 212 because the housing engagement ribs 292 (FIG.36A) are engaged with three of the shuttle lock peripheral teeth 280(FIG. 33).

After the units wheel has reached dose “9”, in stage 2 (FIG. 35B andFIG. 37), the drive dogs 261 of the units wheel 218 engage shuttle lockdogs 282 during dose “10”. The engagement of the angled faces of thedogs 261, 282, causes a camming action that moves the shuttle lock 222axially rearwardly enough to disengage the shuttle lock peripheral teeth280 from the housing engagement ribs 292. The shuttle lock 222 istherefore no longer rotationally locked to the housing 212. Since thekey 273 is axially moveable in the keyway 281, the shuttle lock 222 isable to move axially relative to the tens wheel 219. Consequently, thetens wheel 219 itself does not move axially and the tens numbers 270remain in a position adjacent to the units numbers 260. The axiallyrearward movement of the shuttle lock 222 causes angled faces of thedogs 261, 282 to reach the end of their sloping engagement, at whichpoint the shuttle lock rear teeth 283 engage the axially-extendingsplines 262 on the units wheel 218. This rotationally locks the unitswheel 218 and the shuttle lock 222 together.

The units wheel 218 is still able to turn. The tens wheel 219 is stillrotationally locked to the shuttle lock 222 by virtue of the key 273engaging in the keyway 281. Because the shuttle lock 222 (and hence thetens wheel 219 rotationally locked thereto) is rotationally locked tothe units wheel 218 by the engagement of the units wheel splines 262with the shuttle rear teeth 283, further turning of the units wheel 218causes the shuttle lock 222 and the tens wheel 219 to rotate together.

After 9° of rotation of the shuttle lock 222 and tens wheel 219 by theunits wheel 218, stage 3 is reached (FIG. 35C and FIG. 38), in which twoof the shuttle lock peripheral teeth 280 come into contact with theangled faces of the two housing dogs 291.

Then, for the next 9° of rotation, the camming action of the angledfaces of the housing dogs 291 and those of the shuttle lock peripheralteeth 280 cause the shuttle lock 222 to revert axially to re-engage thehousing engagement ribs 292 so that the shuttle lock 222 is once againrotationally locked to the housing 212. Axial reversion of the shuttlelock 222 to its stage 1 forward position also causes the shuttle lockrear teeth 283 to disengage from the splines 262 on the units wheel 218.In this example, for every 18° of rotation (9° +9°), the shuttle lockcompletes a full cycle as described above. Other angles of rotation foreach cycle are possible.

This completes the number change of the tens wheel 219. The mechanismfunctions in reverse if the dose is decremented.

Dose Setting—Maximum/Minimum Dose Limit

Limiting the maximum/minimum dose that can be set by the dose selector216 is realised by cut out features 271, 272 on the tens wheel 219 whichinteract with a limit rib 290 on the housing. One side of the rib 290limits the tens wheel at the minimum dose when feature 272 is rotatedinto abutment with the rib 290 (FIG. 39A). The other side of the rib 290limits the tens wheel at the maximum dose, typically 100 IU, whenfeature 271 is rotated into abutment with the rib 290 (FIG. 39B). Asmentioned above, the rib 290 is an extended part of one of the housingdogs 291 for engaging the shuttle lock 222.

FIG. 40 is a diagrammatic summary of the key engagement points of theinjection device components, at six stages of dose delivery. Exampledistances of advancement of the dose button 230, starting at 0 mm, areshown. For each distance, each of the hold splines (ratchet pawls 217),drive clutch 250 and drive sleeve 240/drive clutch 250 are indicated asbeing either not engaged (dotted box outline), partially engaged (dashedbox outline) or fully engaged (solid box outline).

As with the first embodiment, described with reference to FIGS. 1-3, thedrive spring 220 is coupled to the units wheel 218 such that a chargingforce can be transferred from the dose selector 216 to the spring 220via the units wheel 218 to increase the energy stored by the spring 220.By coupling the spring 220 to the units wheel 218, a more accurate doseindication may be achieved. When the dose selector 216 is rotated by auser, the dose indicator (units wheel 218 and tens wheel 219), which isin series therewith serves a dual function of both displaying thecurrently selected dose and also transferring the charging force fromthe dose selector in order to charge the drive spring 220.

Throughout the description and claims of this specification, the words“comprise” and “contain” and variations of them mean “including but notlimited to”, and they are not intended to (and do not) exclude othermoieties, additives, components, integers or steps. Throughout thedescription and claims of this specification, the singular encompassesthe plural unless the context otherwise requires. In particular, wherethe indefinite article is used, the specification is to be understood ascontemplating plurality as well as singularity, unless the contextrequires otherwise.

Features, integers, characteristics, compounds, chemical moieties orgroups described in conjunction with a particular aspect, embodiment orexample of the invention are to be understood to be applicable to anyother aspect, embodiment or example described herein unless incompatibletherewith. All of the features disclosed in this specification(including any accompanying claims, abstract and drawings), and/or allof the steps of any method or process so disclosed, may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive. The invention is notrestricted to the details of any foregoing embodiments. The inventionextends to any novel one, or any novel combination, of the featuresdisclosed in this specification (including any accompanying claims,abstract and drawings), or to any novel one, or any novel combination,of the steps of any method or process so disclosed.

The reader's attention is directed to all papers and documents which arefiled concurrently with or previous to this specification in connectionwith this application and which are open to public inspection with thisspecification, and the contents of all such papers and documents areincorporated herein by reference.

REFERENCE NUMERALS

-   10 injection device-   L longitudinal axis-   10 a front end of the device-   10 b rear end of the device-   12 housing-   12 a aperture in the housing-   14 needle-   16 dose selector-   16 a first plurality of teeth on dose selector-   18 dose indicator-   18 a second plurality of teeth on dose indicator-   20 spring-   20 a first end of the spring-   20 b second end of the spring-   22 drive assembly-   24 medicament container-   26 force path-   100 injection device-   L longitudinal axis (housing)-   Lc second longitudinal axis (cartridge)-   100 a front end of the device-   100 b rear end of the device-   107 units housing feature-   108 tens housing feature-   109 housing ridge features-   110 housing smooth inside surface track-   111 housing ramps for drive shaft ratchet arms-   112 housing-   112 a aperture in the housing-   113 housing teeth-   114 tabs-   115 dose selector pawl-   116 dose selector-   117 dose indicator spring-   118 units wheel-   118 a teeth on units wheel (for engaging tens wheel)-   118 b formation on units wheel (for engaging units housing feature)-   119 tens wheel-   119 a teeth on tens wheel (for engaging units wheel)-   119 b formations on tens wheel (for engaging tens housing feature)-   120 drive spring-   124 medicament cartridge-   125 cartridge holder-   126 cartridge stopper-   130 dose button-   131 dose button spring-   140 drive shaft-   141 dose limit nut-   141 a dose limit nut endstop feature for max dose limiting and last    dose limiting-   141 b dose limit nut endstop feature for min dose limiting-   142 worm gear-   143 worm gear support-   144 worm gear rotational lock-   145 plunger rack-   146 drive shaft ratchet arms-   147 max dose endstop on plunger rack for dose limit nut-   148 min dose endstop on plunger rack for dose limit nut-   149 drive shaft splines-   150 worm gear clutch-   A backlash point for over-torque protection-   200 injection device-   200 a front end of the device-   200 b rear end of the device-   L longitudinal axis-   212 housing-   212 a aperture in housing-   213 housing teeth-   214 tabs on housing-   215 clutch engaging feature on housing-   216 dose selector-   217 ratchet pawl-   217 a ratchet fingers-   217 b ratchet arms-   218 units wheel-   218 a units wheel ribs-   219 tens wheel-   220 drive spring-   221 housing top cap-   222 odometer shuttle lock-   224 medicament cartridge-   225 cartridge holder-   226 cartridge stopper-   230 dose button-   231 dose button spring-   240 drive sleeve-   240 a last dose nut endstop-   241 last dose nut-   250 drive clutch-   250 a haptic feedback arm-   251 drive clutch spring-   252 leadscrew nut-   253 leadscrew-   254 thrust bearing-   260 units numbers-   261 units wheel drive dogs-   262 units wheel engagement splines-   270 tens numbers-   271 max dose limit feature-   272 min dose limit feature-   273 tens wheel key to engage shuttle lock-   280 shuttle lock peripheral teeth-   281 shuttle lock keyway-   282 shuttle lock dogs-   283 shuttle lock rear teeth-   290 housing max/min limit rib-   291 housing dogs for engaging shuttle lock-   292 housing engagement ribs-   A backlash point for dose decrementing

1. An injection device comprising: a. a housing having a longitudinalaxis; b. an axially-depressible dose button; c. a dose indicatorcomprising an odometer positioned within the housing and arranged aboutsaid longitudinal axis; d. a dose selector operatively connectable tothe dose indicator, the dose selector and the dose indicator beingcapable of cooperating with one another to set a dose to be ejected fromthe injection device; and e. a spring capable of storing energynecessary for ejecting the dose from the injection device; wherein thespring is locked at one end to the dose indicator such that a chargingforce can be transferred from the dose selector to the spring via thedose indicator, when the dose selector is operatively connected to thedose indicator, to increase the energy stored by the spring.
 2. Theinjection device of claim 1 wherein the dose selector is operativelyconnectable to the dose indicator via a ratchet pawl, the ratchet pawlreleasably engaging the dose selector and preventing counter-rotation ofthe dose indicator during dose setting, the ratchet pawl beingdisengageable from the dose selector by axial depression of the dosebutton.
 3. The injection device of claim 2 wherein said charging forcecan be transferred from the dose selector to the spring via the engagedratchet pawl and dose indicator.
 4. The injection device of claim 1wherein the spring is a torsion spring and the charging forcetransferred to the spring is a charging torque.
 5. The injection deviceof claim 4 further comprising a drive assembly having a rotational toaxial coupling, where the drive assembly is rotationally drivable by thetorsion spring and is arranged to provide an axial force for ejectingthe dose from the injection device.
 6. The injection device of claim 5wherein the drive assembly is rotationally drivable by the torsionspring via the dose indicator.
 7. The injection device of claim 1wherein the spring is directly locked to the dose indicator.
 8. Theinjection device of claim 1 wherein the spring is locked to the doseindicator via one or more intermediate components capable oftransmitting the charging force.
 9. The injection device of claim 1wherein the dose selector is directly coupled to the dose indicator. 10.The injection device of claim 1 wherein the dose selector is coupled tothe dose indicator via one or more intermediate components capable oftransmitting the charging force.
 11. The injection device of claim 1wherein the dose indicator is marked with a sequence of numbers orsymbols, at least one of the numbers or symbols being visible through anaperture or window in the housing.
 12. The injection device of claim 1wherein the odometer comprises: a. a units wheel operatively connectedto the dose selector so that rotation of the dose selector also rotatesthe units wheel, and b. a tens wheel selectively engageable with theunits wheel so that rotation of the units wheel also rotates the tenswheel.
 13. The injection device of claim 1 further comprising amedicament container.
 14. The injection device of claim 13 wherein themedicament container comprises a pre-filled syringe or cartridge. 15.The injection device of claim 13 further comprising a medicamentcontained in the medicament container.
 16. The injection device of claim15 wherein the medicament is selected from the group comprising:antipsychotic substances including risperidone, hormones, antitoxins,substances for the control of pain, immunosuppressives, substances forthe control of thrombosis, substances for the control or elimination ofinfection, peptides, proteins, human insulin or a human insulin analogueor derivative, polysaccharide, DNA, RNA, enzymes, antibodies,oligonucleotide, antiallergics, antihistamines, anti-inflammatories,corticosteroids, disease modifying anti-rheumatic drugs, erythropoietin,or vaccines, for use in the treatment or prevention of rheumatoidarthritis, psoriatic arthritis, ankylosing spondylitis, ulcerativecolitis, hormone deficiency, toxicity, pain, thrombosis, infection,diabetes mellitus, diabetic retinopathy, acute coronary syndrome,angina, myocardial infarction, atherosclerosis, cancer, maculardegeneration, allergy, hay fever, inflammation, anaemia, ormyelodysplasia, or in the expression of protective immunity.